anyone have a similar problem with their sigma rox 5.0 heart rate monitor?

mine refuses to 'refresh' on a consistent basis. i can be pedaling comfortably and the read-out will register, say, 132. i can stand and pedal hard up an incline and the read-out continues to register the same 132 when suddenly, perhaps near the top of the incline, it will jump to 184. when i coast downhill at resting pace it will jump back down to, say, 124, but not incrementally, just suddenly.

i called rox and the technician suggested moving the chest strap closer to the heart side of my chest, which i did but to no avail. i use electrode gel which seems to help but just a bit. the only other chest monitor i used in the past was for running years ago; it was a polar brand and i did not have this problem. i got constant updates on the wrist monitor. that's why i'm wondering what is wrong with the rox monitor. this problem with the rox makes it pretty much useless. it also will not record an accurate 'maximum heart rate' for rides.

anyone have any idea about what's happening and any suggestions for correction? do all bike monitors behave like this?